Method and system for gas stunning of poultry for slaughter

ABSTRACT

A method for gas stunning of poultry for slaughter is described, where the poultry arrives at the poultry slaughterhouse in for example in transport crates, where gas stunning of the animals is effected after the animals have been taken out of the transport crates, and where the animals by means of a number of conveyors ( 18, 20, 24, 32 ) are conveyed successively through a stunning chamber ( 8 ), where the influence of the gas for stunning of the animals is adjusted by reducing or prolonging the conveying time and/or the conveying route of the animals on said conveyors through the stunning chamber ( 8 ).

FIELD OF THE INVENTION

The present invention relates to a method for gas stunning of poultryand of the kind stated in the preamble of claim 1.

BACKGROUND OF THE INVENTION

Over time, many different methods have been proposed for gas stunning ofpoultry arriving at the poultry slaughterhouse in transport crates, withno remarkable success. In practice however, several parameters must beconsidered in order to be able to optimise a method for gas stunning ofpoultry for slaughter.

To optimise the method, the following parameters must be considered:

-   -   Conveying speed (capacity of the system).    -   Size and number of birds in the transport crates.    -   The physical condition of the poultry flock which is determined        by continuously observing variations in stress condition or        resistance of the poultry which are significant for determining        the time necessary for stunning the poultry which further may        vary because of conditions in broiler houses, temperatures,        transport time, and waiting time in the slaughterhouse.

To optimise the gas stunning it is furthermore necessary to be able tocontinuously consider all these parameters prior to and during gasstunning of the poultry supplies delivered to the slaughterhouse, andcontinuously apply the most advantageous parameters to achieve optimumgas stunning of the actual chicken flock at any time to be stunned andslaughtered, respectively.

To optimise these parameters, different periods of stunning time can beapplied, but variations in the gas concentration, and variations of gasconcentration in the different sections of the conveying route must alsobe considered, dependent on the conveying route length and conveyingroute location in the stunning chamber.

The gas concentration may be monitored and controlled by means ofsensors having different locations, and a PLC control system. Adjustmentof the stunning time and simultaneous variation of the gas concentrationrequire a change in the previously used methods by which a givenslaughtering capacity of number of birds per minute required a fixedconveying time through stunning chamber. A given rate of slaughtering(slaughtering capacity) will always be determined by other subsequentparameters that cannot be changed right away why they are maintained.Consequently it may furthermore be necessary to be able to change thedegree of stunning, depending on the condition of the poultry uponarrival at the slaughterhouse and unloading for slaughter.

PURPOSE OF THE INVENTION

On this background it is the purpose of the invention to provide animproved method for gas stunning of poultry for slaughter, which methodby means of simple provisions and means makes it possible to optimisethe stunning by being able to allow for all the parameters mentioned.

BRIEF DESCRIPTION OF THE INVENTION

The method according to the invention is characterised in that theinfluence of the gas for stunning of the animals is adjusted by reducingor prolonging the conveying time and/or the active conveying routelength of the animals on said conveyors through the stunning chamber. Ithas surprisingly appeared that by means of such simple provisions it ispossible to optimise the stunning, while at the same time allowing forall the parameters mentioned. As an especially important thing it shouldbe mentioned that at the same time it is possible to consider thewelfare of the animals by observing the stunning condition of theanimals before they reach the actual slaughter. If the stunningcondition of the animals is not optimum, it will be easy to prolong orreduce the conveying time and/or the conveying route through thestunning chamber.

An optimum condition of stunning will be that the animals are so wellstunned that with certainty they do not awaken before they reachslaughtering. On the other hand it is also important that the animals donot die in stunning because it is important that the pump function ofthe heart is maintained in order to contribute to the pumping out ofblood when the necks of the animals are cut in the actual slaughter.

Appropriately, by the invention a method is used by which the adjustmentof the conveying time through the stung chamber is effected byincreasing or reducing the speed of the said conveyors.

By the method according to the invention it may furthermore beadvantageous that the adjustment of the conveying route through thestunning chamber is effected by reducing or prolonging the activeconveyor runs of the respective conveyors.

Furthermore, the method according to the invention may be modified suchthat the influence of the gas for stunning of the animals moreover isadjusted by varying the gas concentration at varying heights in thestunning chamber in that increasing gas concentration is applied in adirection downwards in the stunning chamber.

The invention furthermore relates to a system for gas stunning ofpoultry for slaughter cf. the method according to claim 1, andcomprising a substantially horizontal conveyor arranged for receivingand into poultry for slaughter to a gas-filled stunning chamber in whicha downwards running conveyor is arranged, which conveyor is arranged forsuccessively conveying the poultry downwards in the stunning chamber,and an upwards running conveyor arranged for successively conveying thepoultry upwards and out of the stunning chamber, said system beingcharacterised in that said downwards running conveyor either isconstituted by a conveyor having a downwards running course and ahorizontal course, and by a downwards running conveyor, said conveyorscomprising mutually interacting telescopic members for adjustment of theactive conveying route length, or are constituted by a helical conveyorinteracting with a horizontal, telescopic conveyor.

Preferably, the system according to the invention is provided such thatsaid upwards running conveyor is constituted by conveyors havingmutually interacting telescopic members, viz. a horizontal conveyor andan upwards running conveyor having a slanting course.

Appropriately, the system according to the invention is provided suchthat the stunning chamber is divided into a number of horizontal zones,e.g. a lower zone having a gas concentration (CO²) of 50% (app. 45-51%),an intermediate zone having a gas concentration (CO²) of 25% (app.32-46%), and an upper zone having a gas concentration (CO²) of 5% (app.8-10%), in that sensors are provided in level with the upper zone limitsfor monitoring and control respectively of the gas concentration in thesaid zones. The actual gas concentration percentage varies a great dealin connection with shift between pause and operation, and upon changedrate of motion of the animals. This variation in gas concentration hasrelatively small influence on the stunning result, whereas the time ofpresence, especially in the first zone, and the total time of presencein the stunning chamber have great influence.

The system according to the invention is preferably provided such thatit comprises a PLC control system for controlling a number of mutuallydependent mechanical parameters, for example speed of conveyors, setting(17.6 metres/minute), number of birds (chickens) on conveyors, speed ofslaughtering line, setting (148 animals/minute).

If one setting is changed, the other settings are changedcorrespondingly, for example if the birds are larger, it means thatthere are fewer animals on the conveyors, but the speed of theslaughtering line continues to be the same. Consequently it becomesnecessary to convey more animals per minute through the stunningchamber, i.e. increased conveying speed. At the same time eachindividual bird is larger why it is stunned for a longer time, i.e.longer conveying time and conveying route length respectively arerequired through the stunning chamber.

BRIEF DESCRIPTION OF THE DRAWING

The invention is explained in more detail below with reference to thedrawing in which

FIG. 1 shows a longitudinal sectional view, partially in section,through an embodiment of a system for gas stunning of poultry forslaughter according to the invention, and

FIG. 2 shows a top view of another embodiment of a system for gasstunning of poultry for slaughter.

DETAILED DESCRIPTION OF THE INVENTION

The system 2 shown in FIG. 1 for gas stunning of poultry for slaughtercomprises a supply conveyor (not shown) for supply of poultry, which forexample arrives at the slaughterhouse by truck, and which have beentaken out of any transport crates before they are transferred to thestunning system 2. The poultry 4 is transferred successively to astunning conveyor 6 which actually consists of a system of endlessconveyors having a number of sections running downwards into a stunningchamber 8, the major part of which consists of a concrete pit 10 loweredin relation to the floor level, which chamber is filled with stunninggas, for example CO² with varying gas concentrations, viz. an upper orfirst zone 12 having a gas concentration of app. 5% (8-10%), anintermediate or second zone 14 having a gas concentration of app. 25%(32-46%), and a lower and third zone 16 having a gas concentration ofapp. 50% (45-51%).

The gas concentration in the said zones 12, 14, 16 can be further variedaccording to requirements, for example in relation to bird size or type.The gas concentration in the respective zones is controlled by suitablegas sensors and an actually known gas filling/control system withfilling valves.

From the stunning conveyor 6 the poultry 4 is successively conveyed intoa downwards running conveyor section 18, which continues into ahorizontal conveyor section 20, whose active length can be varied bymeans of a telescopic system 22. From the conveyor section 20 thepoultry 4 is transferred to a downwards running conveyor section 24whose active length can be varied by means of a telescopic system 26which interacts with the telescopic system 22 for the conveyor section20. From the conveyor section 24 the poultry 4, which by now is stunned,is conveyed onto a horizontally ring conveyor 28 whose active conveyingroute length also can be varied by means of a telescopic system 30. Thestunned poultry 4 is then conveyed upwards and out from the stunningchamber 8 by means of an upwards running conveyor 32, which, and forbeing able to interact with the conveyor 26, also comprises a telescopicsystem 34 for variation of the active conveying route length of theconveyor 28.

From the conveyor 32 the stunned poultry is transferred to an externalconveyor for being shackled on a slaughtering line. Shortly after thestunned chickens have been shackled by their legs in slaughter shackles,the chickens pass a slaughter location where their necks are cut so thatthe chickens bleed out as the pumping function of their hearts is stillintact if the gas stunning was optimum.

If it can be found that the gas stunning either is too deep, that is thechickens are already dead, the stunning must be adjusted by shorteningthe conveying route and/or the conveying time through the stunningchamber so that the stunning becomes lighter. If the chickens on thecontrary show signs of too light stunning, the stunning must likewise beadjusted so that the conveying route and/or the conveying time throughthe stunning chamber are increased.

In both situations, adjustment can be effected by reducing or prolongingthe conveying time and/or by changing the active conveying route lengthsof the conveyors 20, 24, 28, 32 by means of the telescopic systems 22,26, 30, 34.

Sensors in given locations ensure that the respective conveyors are incorrect positions, for example for small, medium-sized, or largechickens. An important thing which also influences the stunning resultis that the poultry 4 is downwards step by step, starting in a low gasconcentration of app. 5-10%. The stepwise downwards conveying ensuresthat the chickens upon start and stop lift their heads whereby they canfreely breathe in the relatively low gas concentration. This preventsthe poultry from becoming stressed and injuries are avoided.

To reduce or prolong the conveying time through the stunning chamber 8,it is of course also possible to adjust the speed of the respectiveconveyors.

After the first part of the downwards movement, the poultry has “fallenasleep” and this continues further down where the gas concentration ismax. 50% at the bottom of the chamber. Hereby it is ensured that thechickens will not wake up before their necks have been cut and they havebled out. As regards safety it is furthermore an advantage to lower thestunning chamber to below floor level so that gas leakage above headheight is avoided.

The system 36 outlined in FIG. 2 comprises a stunning chamber 38 whichlike the system 2 (FIG. 1) described above comprises a concrete pit 40lowered in relation to floor level. After unloading, poultry istransferred to the stunning chamber 38 via a horizontal supply conveyor42 delivering the bird to a downwards running helical conveyor 44 whichat the bottom of the stunning chamber 38 again delivers the now stunnedbird to a horizontal, telescopic conveyor 46 from which the stunned birdis transferred to an upwards running conveyor 48 which conveys thestunned bird upwards and out of the stunning chamber 38 for furtherconveyance to shackling on a slaughtering line, etc.

The conveyors 42, 44, 46 have relatively large widths of for exampleapp. 800 mm each, that is at a given speed, the capacity of theseconveyors is large. In a simple manner the width of the conveyors 42,44, 46 and thus their capacity can be reduced by means of laterallydisplaceable walls 43, 45, 47. By this lateral displacement of the walls43, 45, 47 the conveying route length is moreover varied in that thelength of the helical conveyor is prolonged by forcing the poultryoutwards in the curve and oppositely, by forcing the poultry inwards inthe curve.

Alternatively, the capacity of the cooperating conveyors 42, 44, 46 canbe varied by varying the conveying speed or the conveying route lengthin that the number of “twists” of the helical conveyor 44 can beadjusted to the actual conveying need, just as the active length of thetelescopic conveyor 46 can b varied. In this connection, it should bementioned that the slanting position of the upwards running conveyoralso can be adjusted. The upwards running conveyor is provided withtransversely positioned carriers 50 which, if the conveyor 48 has a verysteep course, can be replaced by cups so that the stunned birds willsurely be conveyed upwards and out of the stunning chamber 38.

1. A method for gas stunning of poultry for slaughter arriving at thepoultry slaughterhouse for example in transport crates, where gasstunning of the animals is effected after the animals have been takenout of the transport crates, and where the animals by means of a numberof conveyors are conveyed successively through a stunning chamber,characterised in that the influence of the gas for stunning of theanimals is adjusted by reducing or prolonging the conveying time and/orthe active conveying route length of the animals on said conveyorsthrough the stunning chamber.
 2. A method according to claim 1,characterised in that the adjustment of the conveying time through thestunning chamber is effected by increasing or reducing the speed of saidconveyors.
 3. A method according to claim 1, characterised in that theadjustment of the length of the conveying route through the stunningchamber is effected by reducing or prolonging the active conveyor runsof the respective conveyors.
 4. A method according to claim 1,characterised in that the influence of the gas for stunning of theanimals is moreover adjusted by varying the gas concentration at varyinglevels in the stunning chamber as increasing gas concentration isapplied in a downwards direction in the stunning chamber.
 5. A systemfor gas stunning of poultry for slaughter cf. the method according toclaim 1 and comprising a substantially horizontal conveyor arranged forreceiving and introducing poultry for slaughter to a gas-filled stunningchamber in which a downwards running conveyor is arranged, said conveyorbeing arranged for successively conveying the poultry downwards in thestunning chamber, and an upwards running conveyor arranged forsuccessively conveying the poultry upwards and out of the stunningchamber, characterised in that said downwards running conveyor either isconstituted by a conveyor having a downwards running course and ahorizontal course, and by a downwards running conveyor, said conveyorscomprising mutually interacting telescopic members for adjustment of theactive conveying route length, or are constituted by a helical conveyorinteracting with a horizontal, telescopic conveyor.
 6. A systemaccording to claim 5, characterised in that said upwards runningconveyor is constituted by conveyors having mutually interactingtelescopic members, viz. a horizontal conveyor and an upwards runningconveyor having a slanting course.
 7. A system according to claim 5,characterised in that the stunning chamber is divided into a number ofhorizontal zones, for example a lower zone having a gas concentration(CO²) of 50% (app. 45-51%), an intermediate zone having a gasconcentration (CO²) of 25% (app. 32-46%), and an upper zone having a gasconcentration (CO²) of 5% (app. 8-10%), as sensors are provided in levelwith the respective upper zone limits for monitoring and controlrespectively of the gas concentration in the said zones.
 8. A systemaccording to claim 5, characterised in that it comprises a PLC controlsystem for controlling a number of mutually dependent mechanicalparameters, for example speed of conveyors, setting (17.6 metresminute), number of birds (chickens) on conveyors, speed of slaughteringline, setting (148 animals/minute).